1. Field of the Invention
This invention relates to the treatment of aqueous media, and more particularly concerns a process for the removal of selected anions dissolved in water.
2. Description of the Prior Art
Several general varieties of exchange resins are well known for the removal of ionic species from water solutions. One type of ion exchange resin, generally referred to as a strong acid type of cation exchanger, is comprised of bead-like particles of cross-linked polystyrene which have been sulphonated so as to contain aromatic sulphonic acid groups. Although such strong acid exchangers have a high capacity for positively charged metal ions, little selectivity is shown in the treatment of multicomponent solutions. Weak acid ion exchange resins, which contain carboxyl groups instead of sulphonic acid groups, likewise demonstrate little specificity in the treatment of multicomponent mixtures.
Specialized polymer products, generally referred to as chelating resins, can selectively absorb ions from solution. However, most such resins have affirmity for only positively charged ions. Similarly, inorganic zeolites, peat moss, and algea cells demonstrate selective absorption characteristics, but are usually effective only with cations.
Exchange resins having affinity for anions are generally comprised of bead-like particles of cross-linked polystyrene containing quaternary ammonium groups. As in the case of cation exchange resins, little selectivity is demonstrated.
U.S. Pat. No. 3,715,339 discloses a gel polymer product for water treatment comprised of a chain of recurring aliphatic amine groups, and pendant carboxyl groups. Although having the ability to absorb certain ions from aqueous solutions, the polymer product, without special modifications and critically chosen conditions of use, performs poorly in selectively absorbing anions.
It is accordingly an object of the present invention to provide a process for the selective removal of anions from aqueous solutions.
It is another object of this invention to provide a process as in the foregoing object which can be rapidly accomplished and which does not affect anions other than those which are selectively removed.
These objects and other objects and advantages of the invention will be apparent from the following description.